Polypeptide therapeutics and in particular antibody-based therapeutics have significant potential as drugs because they have exquisite specificity to their target and a low inherent toxicity. However, they have one important drawback: these are complex, large molecules and therefore relatively unstable, and they are sensitive to breakdown by proteases. Because the degradation they undergo during passage through, for instance, the gastrointestinal tract, administration of conventional antibodies and their derived fragments or single-chain formats (e.g. scFv's) is not very effective. This means that conventional antibody drugs cannot be administered orally, sublingually, topically, nasally, vaginally, rectally or by inhalation because they are not resistant to the low pH at these sites, the action of proteases at these sites and in the blood and/or because of their large size. They have to be administered by injection (intravenously, subcutaneously, etc.) to overcome some of these problems. Administration by injection is therefore the most frequently used method of administration although the method has many disadvantages, for example: (a) poor tolerance by patients, especially when treating chronic disorder; (b) a consequent risk of poor compliance with the dosage when the drug is not a ‘life saver’; (c) difficulty of carrying out self-administration by the patient; (d) possible non-availability of suitable surroundings for carrying out the procedure in an aseptic manner; (e) requires specialist training in order to use a hypodermic syringe or needle correctly and safely. A method for the delivery of therapeutic polypeptides which avoids the need for injection has not only cost/time savings, but would also be more convenient and more comfortable for the subject.
In most animal cells, a specialised pathway is present for uptake of specific macromolecules from the extracellular fluid. The macromolecules that bind to specific cell-surface receptors are internalized, a process called receptor-mediated endocytosis. Receptor internalization is based on the principle of regulation of signal transduction by a process called sequestration, whereby bound agonistic (i.e. receptor activation) ligands are recovered from the cell surface in complex with the receptor. For many applications it is necessary to deliver effector molecules across the cell membrane and into the cytosol. This can be achieved by taking advantage of such internalizing receptors. Antibodies have been described that internalize upon binding to internalizing receptors. However, they have important drawbacks: these antibodies are complex, large molecules and therefore relatively unstable, and they are sensitive to breakdown by proteases. Moreover, the domains of such antibodies are held together by disulphide bonds that dissociate in the reducing environment of the cytoplasm leading to a substantial loss of binding activity. Therefore, they cannot be used to target intracellular proteins.
Another process that relies on internalisation is the efficient induction of an immune response. In particular, a T-cell response depends heavily on efficient presentation of certain epitopes to the T cells by antigen presenting cells (APCs). In the case of a protein antigen this means that the APC has to take up the protein, internally process it (this is cleaving it) and express certain peptide fragments on its surface in association with MHC (major histocompatibility complex) or HLA molecules. One major and critical event in this process is the efficient uptake of the protein antigen by its APC. Techniques which can enhance antigen uptake by APCs enables an immune response to be elicited against antigens which naturally elicit a weak or no immune response. Therefore, a technique which can boost an immune response against antigenic antigens, naturally weak or non-immunogenic antigens has important implications for vaccination programs.
IgE plays a major role in allergic disease by causing the release of histamine and other inflammatory mediatord from mast cells. A mainstay of treatment of allergic disease, including asthma, is allergen avoidance and treatment of symptoms. Presently, the most effective treatments of allergic diseases are directed towards a regulation of the inflammatory process with corticosteroids. A more direct approach without the negative effects of corticosteroids consists in regulating the allergic process at the level of the initiator of the allergic inflammation, IgE, via an anti-IgE.
The concept of using anti-IgE antibodies as a treatment for allergy has been widely disclosed in the scientific literature. A few representative examples are as follows. Baniyash and Eshhar (European Journal of Immunology 14:799-807 (1984)) demonstrated that an anti-IgE monoclonal antibody could specifically block passive cutaneous anaphylaxis reaction when injected intradermally before challenging with the antigen; U.S. Pat. No. 4,714,759 discloses a product and process for treating allergy, using an antibody specific for IgE; and Rup and Kahn (International Archives Allergy and Applied Immunology, 89:387-393 (1989) discuss the prevention of the development of allergic responses with monoclonal antibodies which block mast cell-IgE sensitization.
Anti-IgE antibodies which block the binding of IgE to its receptor on basophils and which fail to bind to IgE bound to the receptor, thereby avoiding histamine release are disclosed, for example, by Rup and Kahn (supra), by Baniyash et al. (Molecular Immunology 25:705-711, 1988), and by Hook et al. (Federation of American Societies for Experimental Biology, 71st Annual Meeting, Abstract #6008, 1987).
Antagonists of IgE in the form of receptors, anti-IgE antibodies, binding factors, or fragments thereof have been disclosed in the art. For example, U.S. Pat. No. 4,962,035 discloses DNA encoding the alpha-subunit of the mast cell IgE receptor or an IgE binding fragment thereof. Hook et al. (Federation Proceedings Vol. 40, No. 3, Abstract #4177) disclose monoclonal antibodies, of which one type is anti-idiotypic, a second type binds to common IgE determinants, and a third type is directed towards determinants hidden when IgE is on the basophil surface.
U.S. Pat. No. 4,940,782 discloses monoclonal antibodies which react with free IgE and thereby inhibit IgE binding to mast cells, and react with IgE when it is bound to the B-cell FcE receptor, but do not bind with IgE when it is bound to the mast cell FcE receptor, nor block the binding of IgE to the B-cell receptor.
U.S. Pat. No. 4,946,788 discloses a purified IgE binding factor and fragments thereof, and monoclonal antibodies which react with IgE binding factor and lymphocyte cellular receptors for IgE, and derivatives thereof.
U.S. Pat. No. 5,091,313 discloses antigenic epitopes associated with the extracellular segment of the domain which anchors immunoglobulins to the B cell membrane. The epitopes recognized are present on IgE-bearing B cells but not basophils or in the secreted, soluble form of IgE. U.S. Pat. No. 5,252,467 discloses a method for producing antibodies specific for such antigenic epitopes. U.S. Pat. No. 5,231,026 discloses DNA encoding murine-human antibodies specific for such antigenic epitopes.
U.S. Pat. No. 4,714,759 discloses an immunotoxin in the form of an antibody or an antibody fragment coupled to a toxin to treat allergy.
Presta et al. (J. Immunol. 151:2623-2632 (1993)) disclose a humanized anti-IgE antibody that prevents the binding of free IgE to FceRI but does not bind to Fc□R1-bound IgE. Copending WO93/04173 discloses polypeptides which bind differentially to the high- and low-affinity IgE receptors.
U.S. Pat. No. 5,428,133 discloses anti-IgE antibodies as a therapy for allergy, especially antibodies which bind to IgE on B cells, but not IgE on basophils. This publication mentions the possibility of treating asthma with such antibodies. U.S. Pat. No. 5,422,258 discloses a method for making such antibodies.
EP0841946 discloses methods for treating allergic asthma using IgE antagonists.